202 THE CONNECTICUT POMOLOGICAL SOCIETY. 



to contain nothing but the necessary ingredients, and the di- 

 lutions were made with rain water obtained from a cistern. 



General Factors Influencing Spray Injury. 



Without going further into details, it appears at pres- 

 ent that the chief factors concerned in sulphur-arsenical 

 spray injury are: (1) the character of the arsenical; (2) 

 the purity of the sulphur solution; (3) the soundness of the 

 epidermis on foliage and fruit, i.e., its freedom from punc- 

 tures and breaks due to insect or fungous attacks or to 

 previous applications of Bordeaux or lime-sulphur; (4) den- 

 sity and abundance of the application; (5) the size of the 

 drops that collect and the time required for their evapora- 

 tion, suggesting the advisability of moderate applications 

 and avoidance of humid days; (6) differing resistance of 

 varieties ; (7) an apparent seasonal and also locality differ- 

 ence in the resistance of the same varieties; (8) excessive 

 temperatures, — such as resulted in so much scalding of fruit 

 the past season in connection with various sprays applied 

 during the excessive heat, of late June and early July; (9) 

 unknown causes usually attributed to weather conditions. 



Any one of these factors may be the important one in 

 any given case. In general, however, they are probably 

 stated somewhat in order of frequency of importance, at 

 least for the more severe cases. 



The Sulphur-Arsenical Factors. 

 In connection with the first two factors, our peach-spray- 

 ing experiments of the past two years have shown : (1) that 

 when used at proper dilutions, most of the injury from the 

 combined sulphur-arsenical spray is due directly to the arsen- 

 ical, but indirectly to a solvent action of the fungicide; (2) 

 that this solvent action is greatly increased by the pres- 

 ence of caustic substances, such as soda or potash in the 

 spray mixture — a fact which makes it especially dangerous 

 to use either spray water or concentrates that contain ap- 

 preciable quantities of these salts; (3) that certain proprie- 



